OpenEuphoria

2. Re: delegate support in euphoria?

• Posted by DerekParnell (admin) Apr 20, 2012
• 1399 views

Yes. The function routine_id() can be used to get an handle to any procedure or function and then that handle can be passed as an argument to a routine, which would call the handle's routine using either the call_func() or call_proc() as appropriate.

As an example, the custom_sort() function expects you to pass a routine_id as the comparison algorithm.

Here is an example of your 'retain' idea.

function odd_val(object X) 
	if sequence(X) then 
		return 0 
	end if 
	 
	if integer(X) then 
		return and_bits(X,1) 
	end if 
	 
	return 0 
end function 
 
function multiple_3(object X) 
	if sequence(X) then 
		return 0 
	end if 
	 
	if integer(X) then 
		return remainder(X, 3) = 0 
	end if 
	 
	return 0 
end function 
 
 
function retain(sequence A, integer criteria) 
	sequence temp 
	integer p = 0 
	 
	temp = repeat(0, length(A)) 
	 
	for i = 1 to length(A) do 
		if call_func(criteria, {A[i]}) then 
			p += 1 
			temp[p] = A[i] 
		end if 
	end for 
	 
	return temp[1.. p] 
end function 
 
sequence testdata = {1,2,3,4,5,6,7,8,9,10,11,12} 
 
? retain(testdata, routine_id("odd_val"))    --> {1,3,5,7,9,11} 
 
? retain(testdata, routine_id("multiple_3")) --> {3,6,9,12} 

4. Re: delegate support in euphoria?

• Posted by kobi Apr 22, 2012
• 1347 views

function odd_val(object X) 
	if sequence(X) then 
		return 0 
	end if 
	 
	if integer(X) then 
		return and_bits(X,1) 
	end if 
	 
	return 0 
end function 
 
function multiple_3(object X) 
	if sequence(X) then 
		return 0 
	end if 
	 
	if integer(X) then 
		return remainder(X, 3) = 0 
	end if 
	 
	return 0 
end function 
 
 
function retain(sequence A, integer criteria) 
	sequence temp 
	integer p = 0 
	 
	temp = repeat(0, length(A)) 
	 
	for i = 1 to length(A) do 
		if call_func(criteria, {A[i]}) then 
			p += 1 
			temp[p] = A[i] 
		end if 
	end for 
	 
	return temp[1.. p] 
end function 
 
sequence testdata = {1,2,3,4,5,6,7,8,9,10,11,12} 
 
? retain(testdata, routine_id("odd_val"))    --> {1,3,5,7,9,11} 
 
? retain(testdata, routine_id("multiple_3")) --> {3,6,9,12} 

Thanks! is there a benefit for initializing the sequence with repeat? (the alternative is starting with an empty sequence and appending an element every time) is the data structure (beneath the sequence) a vector, a dynamic array, some kind of tree, or a simple array that is continuously copied?

another question: is there support for 'assert' in the middle of euphoria code. thanks alot, I enjoy euphoria and appreciate your comments and support

6. Re: delegate support in euphoria?

• Posted by DerekParnell (admin) Apr 22, 2012
• 1303 views

Pre-allocating a sequence is often a good idea for performance. The append operation will usually involve allocating new memory and copying existing items.

There isn't one supplied with the standard library but I think we should have one. Here is the sort of thing you'll need.

-- assert.e 
namespace assert 
 
include std/error.e 
ifdef assert then 
	public procedure assert(integer x, sequence text = "") 
		if x = 0 then 
			crash(text) 
		end if 
	end procedure 
elsedef 
	public procedure assert(integer x, sequence text = "") 
	end procedure 
end ifdef 
 
public procedure ensure(integer x, sequence text = "") 
	if x = 0 then 
		crash(text) 
	end if 
end procedure 

You can include this file and then use the assert() routine to test your logic at run-time, but only if the 'assert' symbol has been defined on the command line. For example ...

-- mytest.ex 
include assert.e 
 
integer a 
a = 5 -- An obvious error. 
assert(a = 4, "'a' should be 4") 
? a 

When you run this normally, the assertion will not execute because the 'assert' symbol was not defined.

C:\temp> eui mytest.ex 
5 
C:\temp 

C:\temp>eui -d assert mytest.ex 
 
c:/Projects/eu_proj/eu40/include\std\error.e:50 in procedure crash() 
'a' should be 4 
 
... called from C:\temp\assert.e:8 in procedure assert() 
 
... called from C:\temp\mytest.ex:5 
 
--> See ex.err 
 
C:\temp> 

Because the assert() routine is very small, Euphoria will automatically in-line it so there is no overhead of a function call, and when the 'assert' symbol is not defined, the in-lined code is totally no-existant, thus it has no run-time performance affect.

The ensure() routine is identical to assert except that it doesn't need the 'assert' symbol to be defined. You would use ensure to ensure a condition was tested in production releases of code and use assert for tests that should not be in production releases development. This especially applies to translated programs.

8. Re: assert in EUPHORIA

• Posted by DerekParnell (admin) Apr 22, 2012
• 1393 views

type truth_type(integer x) 
    return x = 1 
end type 
 
public truth_type truth 

-- buffer should have no more nulls 
truth = find(0,buffer) = 0 

Although this will perform the testing correctly, it misses out on a couple of the useful aspects of the 'assert' concept.

1. It always executes the test. The assert is intended to only execute the test during the development phase of the application.
2. It's crash message is obscure - type failure - whereas the assert can be given a meaningful message to display.

10. Re: assert in EUPHORIA

• Posted by DerekParnell (admin) Apr 23, 2012
• 1269 views

I see your point. The only way around that at the moment is to code ...

ifdef assert then assert(x) end ifdef 

This is a bit more cumbersome but if you really need it then you can do it.

12. Re: assert in EUPHORIA

• Posted by mattlewis (admin) Apr 23, 2012
• 1253 views

I do something like this in EuSQL. You can set it to do actual error checking or just print errors (or call a user defined routine). And, of course, you can simply turn off type checking to ignore it completely.

Basically, this just handles errors coming back from the library (e.g., bad SQL, incorrect table name, etc.), so there isn't really an expensive performance hit for additional calculations. It's just a relatively simple and informative way to handle error checking.

Matt